In law and in religion, testimony is a solemn attestation as to the truth of a matter. All testimonies should be well thought out and truthful. The words 'testimony' and 'testify' both have a root in the Latin testis, referring to the notion of a third person, disinterested witness. In the law, testimony is a form of evidence that is obtained from a witness who makes a solemn statement or declaration of fact. Testimony may be oral or written, and it is usually made by oath or affirmation under penalty of perjury. Unless a witness is testifying as an expert witness, testimony in the form of opinions or inferences is generally limited to those opinions or inferences that are rationally based on the perceptions of the witness and are helpful to a clear understanding of the witness' testimony.
Contributions by BD2412, Briaboru, and Netesq.